Embodiments of the invention relate generally to auxiliary power assemblies and, more particularly, to a method and apparatus for providing auxiliary power to a locomotive.
Traditional railroad locomotives are powered by diesel-electric power sources, where a diesel engine drives a generator to produce electric power. The output power produced by these engine-generator sets is in turn used to power one or more electric traction motors. The traction motors power the drive wheels of the locomotive.
Locomotives are, by nature, self-contained in that they generate and use the power they require. Typically, locomotive limits are defined by the equipment and fuel that can be carried on the locomotive chassis. Attempts have been made to extend locomotive limits by, for example, attaching a tank car containing fuel (or water) behind a locomotive to give it extended operating range. However, these approaches are of limited utility and are generally not practiced due to harsh operating conditions that limit the ability to distribute locomotive functions across disparate chassis as well as the technical challenges of integrating stock railroad equipment with locomotives.
In recent years, as power needs have grown and railroads have become more concerned about emissions and fuel costs, a variety of approaches have been tried to improve the efficiency of locomotive power.
One such approach is a genset diesel locomotive, which includes a computer-controlled system that manages multiple smaller diesel engines that are turned on and off as power requirements of the railroad locomotive varies.
FIG. 1 illustrates a schematic of an exemplary prior art genset diesel locomotive 10 that includes a locomotive controller 12 that manages multiple engines and additional sensors and inputs. Genset diesel locomotive 10 includes a first engine-generator set 14 and a second engine-generator set 16, both operating in response to locomotive controller 12. Each engine-generator set 14, 16 includes an engine 18, 20 connected to a respective generator 22, 24, which produce electricity for the locomotive traction bus 26 and an auxiliary power bus (not shown). Generators 22, 24 are configured to convert the mechanical energy provided by engines 18, 20 into a form acceptable to one or more traction motors 28 (DC or AC type) configured to drive the axles coupled to the driving wheels 30 of the locomotive 10, and to provide DC or AC power to the respective auxiliary power bus. The amount of power produced by each generator 22, 24 is determined by the engine RPMs and the generator excitation control inputs that are received by generators 22, 24 from locomotive controller 12.
The computer-controlled system for a typical genset diesel locomotive includes an analog electro-mechanical locomotive controller 12 with a throttle control electro-mechanically linked to the controller 12. The controller 12 controls the amount of power generated by the engine-generator sets 14, 16 by varying engine speed and generator excitement in order to produce the desired amount of power on the traction bus 26. In some of these control systems, additional power sensors (not shown), such as load regulators, are used to monitor the fraction bus 26 and/or one or more traction motors 28 and provide input to the controller 12 so it may more accurately manage the engine-generator sets 14, 16. Specifically, the control system uses these sensors for feedback to further govern control of the amount of power generated by the engine-generator sets 14, 16.
Locomotive 10 also includes an engine start and stop control 32 which interfaces with the locomotive controller 12 and is linked to engine-generator sets 14, 16 to initiate their operation and to terminate their operation.
Locomotive 10 also includes engine sensors 34, 36 electrically coupled to engines 18, 20 and the locomotive controller 12. Engine sensors 34, 36 transmit signals 38 to the locomotive controller 12 regarding the status and/or operation of each of the engines 18, 20 (e.g., various parameters of the engines 18, 20 such as RPMs, operating power output, temperature, and other engine status or operating parameters). Locomotive controller 12 transmits control signals 40, including engine RPM settings, generator excitation control inputs, etc., to engine-generator sets 14, 16 to control operation thereof.
In some implementations, engines 18, 20 are operated in response to a throttle position input sensor 42 which indicates the position of the throttle as controlled by the operator at an operator interface 44. In addition, an operator engine start input 46 may be included where the operator can directly or indirectly instruct the locomotive controller 12 (e.g., via a keypad (not shown) located on operator interface 44) with regard to initiation of operation of the engines 18, 20 or termination of operation of the engines 18, 20.
The second to second operation of a locomotive is managed by locomotive controllers. In general, there are two types of locomotive controllers, “traditional” controllers that recognize and control a single engine-generator combination installed on the locomotive chassis, and “genset” controllers, which control a plurality of engine-generator combinations installed on a locomotive chassis. These locomotive controllers manage the production of electricity, provision of the electricity to the power bus, and the generation of tractive effort by traction motors that use the provided electricity. These locomotive controllers also manage fuel use and efficiency, emissions production, and other aspects of the locomotive operation.
In each of these cases, the locomotive controller manages a static, predefined arrangement of one or more engine/generators that provide power to a bus, which in turn provides power to traction motors that move the locomotive. Some locomotive controllers have been configured to control static arrangements of dissimilar power sources (such as an engine-generator, fuel cell, gas turbine, or batteries). These static arrangements have failed due to the lack of operational flexibility required for day-to-day operation of locomotives and/or operational limitations (such as locomotive range, power production limitations, and requiring support for multiple fuel sources). In particular, “genset” style locomotive controllers have not found use in line haul applications because they produce lower overall power than a single, large engine. The amount of power available to the traction motors is a key operational component that characterizes line haul locomotives. Use of dissimilar power source arrangements have failed due cost and operational issues.
Known locomotive controllers also fail to address unexpected signals and operational challenges that become evident when extending the locomotive control and power systems between disparate railcar chassis and integrating power from these external sources with power produced by the engine/generator(s) on the locomotive chassis. As a result, many locomotive power tender configurations have been tried and abandoned due to a number of operational, safety, and related technical issues.
Operational and safety concerns of extended locomotive control and power systems are many and varied. First, locomotive controllers and power tenders may be some distance apart, particularly in consists in which multiple power tenders are utilized. Each rail car is approximately 100 feet in length, and signal degradation, electro-magnetic interference, propagation delays, and related issues are factors when operating a power tender and locomotive together.
Second, extending the power bus (sometimes called a traction bus) between railcars presents similar concerns, not with the signal degradation, but with the cabling and switching apparatus used to safely transport high amperage currents (e.g., 2000 amps) between the power tender and the locomotive fraction bus. Power losses, in particular, voltage losses, arcing, and related issues come into play. Since locomotive power blending is governed by the voltage of the provided power, and is characterized by tight control of the voltage provided to the power bus, losses in voltage or current between a power tender and the locomotive will cause the locomotive controller to improperly manage the combined locomotive/tender. In some cases, these losses will cause the locomotive to not operate. Switching of high amperage power requires Specialty circuitry is also need when switching high amperage power to prevent arcing, contact welding, voltage and amperage spikes and drops, etc.
Third, locomotives and attached power tenders operate in harsh environments. These environments include physical and electro-magnetic challenges. The physical challenges are many and varied; they include widely varied operating temperatures, weather, poor electrical connections between the locomotive and the tender, etc. The control and sensor data is subject to intense electro-magnetic environments (that disrupts the control and sensor data) both external to the consist and within the infrastructure. The shielding required to mitigate these issues described above is itself susceptible to the physical challenges, and degrades over time. Operating a locomotive/power tender in these conditions is challenging.
Fourth, locomotives and their attached power tenders may encounter operational issues, such as connector failure, cable separation, or even chassis separation during regular operation (for example, as would be caused by a coupler failure). Both the locomotive and the attached power tender must safely operate when these conditions occur.
To understand these issues, one must consider both physical and logical constraints of current locomotive consists and locomotive controller architecture.
Railroads have operated many configurations of locomotives and power tenders over the years. Traditionally, locomotive arrangements (herein called a “consist”) include multiple locomotives, linked together using multiple-unit (“MU”) controls. A locomotive consist is the arrangement of locomotives, slugs, and power tenders which are coupled together to provide motive power to a train. One common arrangement is the coupling of two or more independent locomotives together and operating them as a single unit. This arrangement of locomotives has an independent locomotive controller for each locomotive chassis, and shares only throttle setting (an input to a locomotive controller), brake settings, and fault indications. These throttle settings, brake settings, and fault indications are communicated using combination electrical and pneumatic connection commonly referred to “multiple unit” (“MU”).
MU locomotive arrangements are the current operating paradigm for most railroads today. MU locomotives arrangements are characterized by each locomotive having its own independent power generation, distribution (bus), and traction motors. MU controls relay throttle and brake instructions from a first locomotive (master or “A” units) to one or more second locomotives (slaves or “B” units), where these instructions are independently interpreted and tractive effort is provided independently by each locomotive in the consist.
MU locomotives operate independently and do not share power or engine control signals, nor do they permit a first locomotive controller to make requests of a second locomotive controller. Similarly, the locomotive controllers of locomotives operating in MU fashion do not share operational data and do not make operational decisions about the operations of a first locomotive controller based upon the operational characteristics of the second locomotive controller.
Locomotive controllers can be generally characterized as outputting engine control voltages (e.g., RPM and generator excitement voltages), receiving sensor input of operational information (e.g., actual RPM, some fault information, and, in some cases, power bus sensor readings), and then acting to adjust the operation of the engine by varying its control voltages. Locomotive controllers manage the locomotives engines and provide power blending by controlling the amount of power and voltage provided by each engine to the common power bus, which permits the provided power to be combined on the power bus.
Known locomotive controllers are constructed with a basic assumption that the power sources that they control are provided in a fixed arrangement. If a locomotive controller is unaware of multiple possible power sources (e.g., a traditional controller described above), then the use of an external power tender can only be provided on an “all or nothing” basis, where the power tender directly substitutes for the engine-generator on the locomotive chassis. Given the complex nature of locomotive control and the interrelatedness of locomotive loads such as traction motors and blowers, a locomotive's controller, its engine-generator, and an external power tender cannot “share” the generation requirement, with a portion of the power coming from the engine-generator, and remainder of the power coming from the external power tender without the locomotive controller being aware of the power tender and the amount of power it produces. The locomotive controller will recognize the additional power available on the bus and either fault, mis-control one or more power sources or loads, or even turn off the locomotive's engine-generator. Since other locomotive systems are often tied to the locomotive engine-generator or are utilized proportionally to the amount of power being used by locomotives loads (e.g., blowers, aux power), this results in a non-functioning locomotive.
Specialty locomotive controllers that are aware of multiple power sources also have challenges operating with external power tenders. First, the locomotive controller must be able to handle “power blending,” simultaneously taking part of the required power from a first power source and taking a second part of the required power from a second power source. Specialty controllers that select between one power source or another have the same operational challenges as a traditional locomotive controller (described above). Also, specialty controllers have the operational constraints of each specialty power source hard-coded into their logic and electronics, making changes to the power source configuration hard to impossible.
“Genset” style locomotive controllers are characterized in that they are designed to control multiple engine-generators and to “blend” the power produced by these generators. “Genset” style locomotive controllers typically operate in the DC realm, where they set the power sources to produce differing power amounts at differing voltages, as the blending of power on a common bus is based upon voltage differentials between the power bus and the various power sources (e.g., onboard engine-generators, power tenders). As voltage on the bus drops under load, additional power flows from power sources providing power at voltages about the power bus voltage. Thus, tight voltage control must be used to operate correctly.
Each diesel engine-generator combination is controlled with one set of operational parameters and is controlled by varying run RPM and alternator excitement. Even when engines are placed on disparate railcar chassis, a genset locomotive controller expects that the power tender provides a static, well-known power source that behaves as if it were present on the locomotive chassis. Genset locomotive controllers do not account for the operational issues described above, which lead to no-power, under-power (power not flowing from the power tender to the locomotive power bus), or even whether the power tender is currently attached as part of the consist.
Additionally, genset controllers have built-in assumptions regarding the power curve and engine settings (e.g., RPM, generator excitement) that are used to produce specific power/voltages. These operating assumptions are violated by physical limitations induced by separating the power tender from the locomotive chassis (as described above), and by logical considerations that power tenders may have differ operating parameters and settings (e.g., differing engine type, characteristics, fuels). In current configurations, power tenders and locomotive controllers must be operated as a single, non-varying consist because of inherent limitations in the locomotive control and the lack of locomotive controller knowledge of differing power tenders and each power tenders instructions and operational characteristics.
Newer locomotive power control systems have evolved from electro-mechanical to digital controls offering a variety of new options for power control that perform the same functions as the older electro-mechanical control systems, as well as add new power management and train control functions in order to improve performance and fuel efficiency. However, retrofitting these digital controllers to pre-existing (legacy) locomotives is problematic.
The cost and technical integration challenges of replacing an existing locomotive control system of these older legacy locomotives with a new generation control system are prohibitive. Generally, this requires the wholesale replacement of the locomotive control system and many of the locomotive controls, as well as substantial modifications to the locomotive engine, generator, and other electrical components on the locomotive. Furthermore, these types of changes typically cause a reclassification of the locomotive and require recertification of the locomotive power plant for safety and emissions. The recertification process requires that the engine emissions be updated to current EPA requirements, which adds additional cost. Combined, these costs are prohibitive.
In response to rising fuel costs and tightening emissions controls, attempts have been made to provide alternative power sources for genset diesel locomotives, including replacing the diesel fuel and engine with hydrogen and natural gas powered engines, fuel cells, batteries, and other mechanisms for generating and storing power. While in theory these alternative fuels are capable of producing traction power at a fraction of the cost of a diesel locomotive engine/generator, the use of these alternative power sources pose several challenges for the locomotive industry.
For example, outfitting railroad locomotives with alternative fuel technology incurs expensive infrastructure costs and fueling times. Gaseous fuels, such as hydrogen and natural gas, provide limited range, have limited stored energy, have long refueling times, and require extensive alternative fueling infrastructures. While attempts have been made to add alternative power sources and fuel sources to the locomotive consist, the power and fuel sources are provided in heavy rail containers that require large, container-handling cranes in a rail yard in order to lift containers that house engines and their alternative fuel sources, thereby limiting refueling of alternative fuel locomotives to rail yard locations that support the alternative fuel infrastructure. Further, expensive, rail yard based infrastructure, such as extensive cascades of pressurized tanks are needed to refuel a single set of locomotive tanks. These expensive rail yard infrastructures make the use of these existing technologies untenable. Still further, many alternative locomotive power approaches add substantial amounts of time to refueling and other maintenance operations. For example, the time required to refuel a set of tanks of natural gas is measured in hours, where the time required for fueling a diesel locomotive is closer to fifteen minutes. Fueling times further restrict alternative fuel uses to yard applications such as switchers where the alternative fuel equipment has substantial time available for recharging.
Existing systems also do not recognize the fundamental cost improvement for railroad locomotives that is available is based upon the cost of fuel relative to the amount of energy that is produced by using that fuel, and that other optimizations often are minor in comparison. These systems also fail to recognize that different fuels have different energy content, and that these fuels have different costs depending upon where they are obtained. For example, diesel fuel typically costs more in California than it does on the Gulf Coast, and depending upon market conditions, it may be more efficient to use natural gas, syngas, process gas, diesel, or some other fuel to produce the power required for railroad locomotive use. For these and other reasons, alternative fuel-based power for railroad locomotives has not been accepted by the industry.
Further, retrofitting pre-existing (legacy) locomotive engine controllers for use with alternative fuels is generally cost prohibitive and bring concerns about reliability in these retrofit applications. Current railroad locomotive inventories include many thousands of older locomotives, such as the EMD SD-40 family. The control systems integrated into these pre-existing legacy locomotives typically employ a single engine/generator combination that is controlled with electro-mechanical or simple electronic control systems. The lack of flexibility of these older control systems prohibits the use of newer, more desirable, power sources capable of operating with alternative fuel sources.
In light of the above, it would be advantageous to maintain the ability to operate an existing locomotive engine using the fuel for which it was originally designed while adding the ability provide extra power to that locomotive from an auxiliary power source. Such an approach would allow full redundancy of power generation from more than one fuel and engine/generator, and may in certain situations, allow a controller to provide power to the wheels of more than 100% of the locomotive engine/generator set originally paired with the drive motors.
In light of the above, it would be desirable to design an apparatus and method for providing an auxiliary power source for a locomotive that can be integrated with existing electro-mechanical locomotive controls to provide the benefits of being able to incorporate power from alternative fuel sources with a minimum of rework or recertification of the locomotive power plant or other locomotive systems, such as fans, air conditioning, or additional sensors.
It would further be desirable to design an apparatus and method for refueling a locomotive that permits the use of alternative fuels in easy to use interchangeable delivery systems, where alternatives, such as currently available gaseous fuels, can be provided to railroad locomotives without incurring expensive infrastructure costs and fueling times.
It would also be desirable to design a railroad locomotive that optimizes power usage based upon the costs of available fuel and power requirements, permitting fuel- and power-cost arbitrage within the locomotive and substantially reducing the costs of operating the locomotive.